Case 3 - An Adolescent With Leg Pain

"I'm a 14-year-old athlete going into 9th grade. I play football,
basketball, track, baseball, and wrestling. Football is my favorite
sport and I play linebacker or tackle. On the weekends, I like to
hunt and fish, and do competitive bow-shooting. I live with my mom,
step-dad and my half-brother in a 2-story house out in the country."

The Problem / Clinical Presentation
"I came to the doctor because my right leg's been bothering me for a
while and I haven't been able to run or play sports as much. He took
a look at my leg and made me get an x-ray. Then he sent me to the
University of Iowa to see the cancer doctors."

Rick arrived at the pediatric oncology clinic with his outside
x-rays on a particularly busy day. To expedite the clinic visit,
Rick's films were taken by the pediatric oncologist to the pediatric
radiologist for review. The outside films were of poor technical
quality, and it was decided to repeat them. The findings on the x-ray
could be consistent with several diagnoses, and it was decided to
obtain a complete history and physical before issuing a final x-ray
interpretation.

Rick was somewhat quiet and only after extensive questioning did
he reveal that he had been accidentally hit during track practice by
a shot put a month earlier. He
said that it hurt at first, so he put some ice on it and took
ibuprofen. Since it never bruised, he forgot about it and never told
his parents.

His activity decreased the next few weeks since the track season
was finished, and it wasn't until baseball practice began three weeks
after the incident that his right leg began bothering him again.

Rick complains of pain mainly when he tries to bend his right knee
that he describes as a tearing sensation. He is unable to run
quickly.

Clinical Physical Exam

On physical exam, Rick is a cooperative, quiet adolescent male. As
Rick rests on an exam table that is too short for him, his left leg
dangles off the end and he holds his right leg in a straightened
position . There is an obvious 12 cm x 9 cm area of tenderness and
swelling on the right thigh that is without erythema or warmth. Rick
has passive flexion motion to approximately 90 degrees, and actively
to 45 degrees from a straight line. There was full range of motion in
the right hip and ankle. All other extremities show full muscle
strength and range of motion. When asked to walk, Rick limped
slightly, holding his right leg rigid. There was no lymphadenopathy
or organomegaly and he was hemodynamically stable. The rest of the
physical exam is unremarkable.

Clinical Differential Diagnosis

Osteoid osteoma

Osteosarcoma

Ewing sarcoma

Myositis ossificans

Clinical Labs
No clinical labs were done.

Laboratory Differential Diagnosis
Not applicable

Imaging FindingsAmorphous
calcification is seen in the soft tissues of the right thigh that is
separated from the bone. No abnormal periosteal reaction is seen and
there is normal bony mineralization and bony structure.

Treatment Course, Prognosis and Follow-up
"After the cancer doctors looked at my x-rays, they asked me a lot of
questions, and I remembered to tell them about the shot put. They
told me that I had bleeding in my muscle and now the calcium in my
body is making a hard shell around the blood. They told me I couldn't
play sports until I can bend my leg all the way and I don't have any
more pain. I have to do exercises to make my leg bend better. They
also told me my x-rays would look different for 2-4 years until the
calcium goes away but I should be able to play sports pretty soon."

The Approach to the Adolescent With Leg Pain

Extremity pain is a common problem in all age groups. It may be
difficult to distinguish between bone, muscle, joint or referred
pain. A younger child may not even be able to localize the pain.

Differential Diagnosis
The differential diagnosis changes with the age, history and physical
examination of the patient.

In infancy and toddlerhood (see also childhood and
adolescence)

Transient synovitis

Septic arthritis/osteomyelitis

Hypermobility

Diskitis

Trauma

Child Abuse

Neoplasia (including leukemias and metastatic disease)

Juvenile rheumatoid arthritis

Referred pain

Rubella

In childhood (see also infancy and toddlerhood and adolescence)

Sickle cell pain crisis

Neoplasia (including primary bone tumors)

Legg-Calve-Perthes Disease

Serum sickness

Henoch-Schonlein purpura

Collagen vascular diseases (SLE, dermatomyositis,
sarcoid)

Rheumatic fever

Drugs

Porphyria

Caffey's Disease

Spondyloarthropathy

Psychological/Behavioral

Non-specific limb pain such as "growing pains"

Abdominal abscess

In adolescence (see also infancy and toddlerhood and childhood)

Slipped capital femoral epiphysis (SCFE)

Osgood-Schlatter disease

Sexually transmitted diseases (Syphilis, Neisseria
gonorrhea)

Typhoid fever

Inflammatory Bowel Disease

Osteochondritis

History and Physical
History should include onset of the symptoms, severity, intermittent
or constant pain, and associated symptoms such as limp, refusal to
bear weight, fever and rash. A history of preceding upper respiratory
infections or trauma (especially minor trauma such as a toddler fall
or even new shoes that have rubbed the feet). A close physical
examination of the entire affected limb and proximal areas to the
affected site (looking for sources of referred pain) such as the
shoulder, neck, lower abdomen, pelvis and spine is important.
Inspection for swelling and erythema should be done with palpation of
muscle and bone and notation of localized heat. Additionally, range
of motion of all joints should be noted. A neuromuscular examination
including gait should be assessed. A general physical examination for
signs of systemic infection is also indicated.

Evaluation
The laboratory evaluation could be quite extensive but should be
guided the clinical situation and differential diagnoses being
entertained. Tests to consider are:

Blood

CBC, Differential, Platelet - for infections, malignancy

Blood culture - for bacteremia

ESR - for evidence of inflammation

Imaging

Extremity radiographs - for trauma, primary malignancy

Computed tomography - for better delineation of a bone or soft
tissue lesion

Other

ANA, Rheumatoid Factor - for connective tissue diseases

Total Protein, albumin - for inflammatory bowel disease,
neoplasia

Alkaline Phosphatase, uric acid - for neoplasia

Urethral and cervical cultures - for Neisseria gonorrhea

RPR - for syphilis

Consultation

Orthopaedic Surgery for possible surgical management

Treatment
Most children usually have a self-limited, localized disease process
such as transient synovitis or trauma. These can be treated with
conservative management including rest, limited immobilization,
thermotherapy, and pain relief. More complicated orthopaedic disease
such as Legg-Perthes, and SCFE need orthopaedic management. If an
infectious disease is suspected, appropriate antibiotics should be
administered. Systemic diseases such as connective tissue disease,
inflammatory bowel disease, and neoplasias require a team approach to
the evaluation and management.

Myositis Ossificans Discussion

Clinical Presentation
The most common presentation of Myositis ossificans is in young
athletes after an incident of trauma, but it can be seen at any age.
Minor trauma can result in this benign condition; therefore a
complete history as well as physical is essential to make the
diagnosis. It initially presents as a lesion in the proximal
extremities that is tender and swollen, and later becomes more
well-circumscribed to form a hard but painless mass.

Pathophysiology
Myositis ossificans is heterotopic bone formation. There are several
theories that attempt to explain the development of Myositis
ossificans, but none has been conclusively proven. These include
implantation of periosteum into the muscle, osteogenic cells that
escape the periosteum into the muscle, ossifying hematoma, or
metaplasia of the connective tissue. Myositis ossificans is preceded
by injury that necessitates proliferative repair, and the majority of
these injuries are to the elbow or thigh.

Lab Findings
There are no lab findings commonly associated with the diagnosis of
Myositis ossificans.

Imaging Findings
On plain radiographs, Myositis ossificans appears to be an
irregularly contoured mass that is calcified, with the calcification
becoming initially more dense before beginning to resolve. Although
often in close relationship to bone, there is a radiolucent zone
towards the bone, and no clear connection between the lesion and the
bone. There is no associated periosteal reaction. Computed tomography
will show the lesion to be calcified solely around its periphery,
which allows it to be distinguished from an osteosarcoma which is
completely calcified.

Pathology
A biopsy of the lesion would reveal degenerative necrosis of the
tissue, followed by the invasion of histiocytes. Three zones of
maturity (first described by Ackerman) develop. Zone 1 (central) has
cells with occasional mitotic figures, resembling sarcoma. Zone 2,
the intermediate zone, has immature osteoid formation against a
fibromuscular background. Zone 3, the peripheral zone, consists of
mature peripheral bone with fibrous stroma. Biopsy and histological
examination are not frequently done because at different stages the
specimen may closely resemble osteo-, fibro- or myosarcoma.

Differential Diagnosis

Periosteal osteosarcoma

Extraosseous osteosarcoma

Calcified subperiosteal hematoma

Intraosseous osteosarcoma

Treatment
After a traumatic injury, steps should be taken to prevent the onset
of Myositis ossificans. This includes limiting range of motion
initially (24-48 hours), as any mobilization of the affected muscle
can worsen the development of Myositis ossificans. The next step is
to restore flexion and extension through passive range of motion
exercises. Finally, progressive resistance exercises should be
performed until full range of motion is restored. Mature calcified
masses should be excised if the origin or insertion of the tendon or
muscle is involved, if function is impaired, or if it is a large
lesion that can easily be reinjured.

Prognosis
Myositis ossificans is a benign condition, so with proper treatment
prognosis is excellent.

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